Liquid expulsion device



y 1968 J.P. FEDERER 8 LIQUID EXPULSION DEVICE Filed Sept. 30, 1966 INVENTOR.

JEROME? FEPEPEE United States Patent 3,384,272 LIQUID EXPULSION DEVICE Jerome P. Federer, Canoga Park, Califl, assignor to North American Rockwell Corporation, a corporation of Delaware Filed Sept. 30, 1966, Ser. No. 583,373 7 Claims. (Cl. 222-189) ABSTRACT OF THE DISCLOSURE An expulsion device for expelling gas-free liquid, the system including a smaller tank positioned within a larger tank containing fluid to be expelled and gas for pressurizing the fluid. Adjacent the interior wall .of the smaller tank is a screen which when contacted by liquid forms a surface tension barrier for blocking bubbles of the pressurant gas from penetrating through the barrier. The head holding capacity of the surface tension barrier is independent of and uninfluenced by the volume contained within the larger tank.

This invention relates to a fluid dispensing device and more particularly to a liquid expulsion tank capable .of smoothly expelling an uncontaminated stream of liquid.

It is often necessary in satisfying exacting fluid flow standards to transfer a fluid in a continuous flow and in an uncontaminated state from one location to another. The fluid may, by Way .of example, be liquid fuel to be discharged from a fuel tank to an engine. When the hydraulic system for transferring the fluid is to be used in environments characterized by varying gravitational loads (hereafter referred to as G force), expensive designs or modifications must be made in conventional expulsion devices to minimize or eliminate these conditions capable of disrupting continuous flow. These adverse conditions are experienced by remote controlled model airplanes being maneuvered through loops and turns and also by numerous types of gas generators, such as those in rockets, missiles and the like.

Prior art liquid expulsion devices have numerous deficiencies and are generally incapable of inexpensively achieving continuous flow conditions. One type of expulsion device is characterized by moving parts that must be precisely coordinated and incorporate seals which on changing G force environments are susceptible to rupturing, eroding, and leakage. In addition, a piston-type assembly is inherently expensive, weighty, and occupies an excessive amount of space. Another type of expulsion device incorporates a collapsible bladder which when externally pressurized squeezes fluid contained 'in the de vice through a discharge line. A device of this general type is described in a US. patent application, Ser. No. 559,473, filed June 22, 1966, by DeLacya-Ferris, which application has been assigned to the assignee of the instant application. However, bladders tend to rupture and are further characterized by the deficiency of random folding while being collapsed, which prevents the total quantity of fluid in the device from being expelled. Many of the prior art expulsion devices are incapable of being reused.

The concept of utilizing a surface tension barrier in conjunction with a fluid expulsion device is known as indicated in US. Patent 3,176,882 to J. W. Meermans. This principle is also utilized in the invention described in the previously mentioned Ferris application. However, a serious disadvantage exists when a screen, which when wetted is capable of developing a surface tension barrier, is used as a lining for the interior of the tank containing the fluid to be expelled. The specific disadvantage is that the volume, and to some degree the configuration of the container, is restricted by the liquid head holding capacity of the surface tension barrier. A screen extending over too large an area of the tank would make the surface tension barrier prone to rupture. Then gas bubbles, from the pressurant medium, would become entrained in the outflowing liquid stream causing a potentially harmful, unsteady flow. Thus in these prior art expulsion devices the maximum allowable volume is dictated by the maximum head holding capacity that can be achieved by the surface tension barrier.

The most important aspect of the instant invention is that the dimensions and configuration of the expulsion tank, and hence the maximum fluid volume, are not restricted by the maximum liquid head holding capacity and tensile strength that can be achieved by the surface tension barrier. This is due to the fact that the surface tension barrier is not aligned adjacent to the interior surface of the expulsion tank, as in the case of conventional expulsion tanks. Rather, it is disposed adjacent a portion of the interior periphery of a smaller tank included inside the main liquid-containing tank. Only the dimensions of the smaller tank are dictated by the head holding capacity of the surface tension barrier. Thus, the maximum allowable volume of fluid to be expelled is in no manner a function of the surface tension barrier strength.

Thus the prime object of the instant invention is to provide a fluid expulsion device incorporating a surface tension barrier such that the maximum volume of fluid that can be expelled in the device is independent of the head holding capacity of the surface tension barrier.

Another object of the instant invention is to provide a fluid expulsion device which is reusable and, under certain circumstances, minimizes the harmful effects of sloshing and instability.

These objects as well as additional objects will be readily understood upon studying the following detailed description in connection with the accompanying drawings in which:

FIG. 1 is a partially sectional view showing the main tank and screen trap components of the expulsion device under a G force.

FIG. 2 is a perspective sectional view of the screen trap under a different G force than that of FIG. 1.

FIG. 3 is similar to FIG. 1 and shows the expulsion device under a different G force than that of FIGS. 1 and 2.

In its general aspects, the fluid expulsion device of the instant invention is characterized by a relatively large tank containing liquid to be expelled and a relatively small tank enclosed by the large tank and lined over the major portion of its interior periphery with a screen which when wetted is capable of achieving a surface tension barrier. The space between the screen and small tank forms a shallow chamber. c

When the liquid is pressurized it flows through an inlet line into the small tank, through the shallow chamber, and then outwardly of both tanks through an outlet line. During this action bubbles of gas from the pressurant gas are blocked from entering the outflowing liquid stream by the surface tension barrier which is designed to hold a liquid head sufficient to withstand the maximum predetermined G forces and internal pressurant gas forces. Thus the gas is confined to the interior space of the smaller tank and is incapable of escaping into the shallow chamber. The required volume and configuration of the large tank are wholly independent of the liquid head holding capacity of the surface tension barrier, which capacity can be increased or decreased to accommodate varying requirements.

Referring now to a specific embodiment of the liqui explusion devices of the instant invention, FIG. 1 schematically depicts an expulsion device 10 to be incorporated in a hydraulic system. Expulsion device 10 includes a main tank 12 which totally confines a smaller tank 22 lined over a portion of its interior wall with a screen 40 whose function will be fully described below. Small tank 22 together with screen 40' constitute a unitary structure hereafter referred to as a screen trap 29. This name is descriptive of the fact that screen trap traps liquid to be expelled within a volume defined in part by screen 40. The volume of tank 12 can be of any suitable order of magnitude larger than the volume of screen trap 2i Screen trap 24) is fixed to main tank 12 by anchoring elements 13. Both are constructed from suitable metal such as high strength alloys of aluminum, steel, titanium, or Inconel 718. The choice of which of the above metals or the like is to be utilized is dictated primarily by the environment in which expulsion device 10 is to be used.

Main tank 10 has forward and rearward ends 16 and 17, respectively. An inlet line extends between main tank 12 and screen trap 20 and has an inlet opening 31 and an outlet opening 32. An outlet line 34 extends from inside screen trap 20 to a point outside expulsion device 10 and has an inlet opening and an outlet opening 36.

Initially, a liquid 59 to be expelled is loaded through a port 14 into tank 12 and screen trap 20 so that liquid 54) entirely fills both volumes. Liquid St} is expelled by a constant source of pressurant gas 52 that is continuously exerted on liquid 50. Port 14 can be connected to the source (not shown) supplying gas 52. Expulsion device it) is shown moving forwardly through a gravitational field of intensity G which is being exerted in the direction as shown by the arrow. Gravity force G forms a flat surface 51 which is normal to the arrow. Pressurized liquid 50 flows smoothly in a continuous path through inlet 31 of inlet line 30, into screen trap 20 and then outwardly through line 34 to a remote location.

Referring to FIG. 2, a longitudinal sectional view is shown of additional details of screen trap 20. Small tank 22 has a fiat top wall 25, an arcuate bottom wall 24 and semi-circular forward and rearward walls 26 and 27 re spectively, all of which are secured together as a unit. Numerous adequate configurations of tank 2-9 could be designed. When the vehicle or the like incorporating expulsion device it} is in motion, the forward wall 26 constitutes the leading end. Screen is maintained in slightly spaced relationship adjacent to walls 24, 25, and 26. Screen 4%), which is of very fine mesh in the order of 8 microns, for example, is pulled taut and held in fixed spaced relationship from the adjacent walls. This can be achieved by any suitable supporting framework (not shown), which may include anchoring tie lines, weld beads, or the like. An edge 41 of screen 4% is fixed in fluid-tight relationship to the inner periphery of rearward wall 27. Another edge 42 of screen 46 is fixed in fluid-tight relationship to inlet opening 35 of outlet line 34. The space defined by the interior wall of screen 46 and rearward wall 2'7 constitutes a reservoir 42. The space defined by the exterior surface of screen 40 and walls 24, 25, and 26 constitutes a shallow chamber 46. Chamber 46 together with outlet line 34 provide a continuous discharge conduit for fluid 50 collected in reservoir 42.

The interrelationship of liquid 50 and pressurant gas 52, as shown in FIG. 2, represents one of the most adverse G force conditions to be encountered by expulsion device 10. A high G force, G acting in a direction as indicated by the arrow, is being exerted on liquid 50 forcing it to assume a shape with a flat, sloped surface 55. Surface lies in a plane perpendicular to the direction in which gravity force G is being exerted. When, due to sloshing of liquid 50 for example, inlet opening 31 becomes exposed to pressurant gas 52, a pocket of pressurant gas 53 from source 52 will become collected in reservoir 42. Bubbles from this pocket will attempt to become entrained or otherwise added to the outflowing liquid.

An important aspect of this invention is to prevent bubbles from gas 53 from entering into shallow chamber 46 from which position they would be added to the outflowing liquid stream and would thereby interrupt the desired continuous flow. Such an undesirable result is prevented by screen 40 and a film from liquid 5%"! which together cause the necessary surface tension barrier. Before discussing how the surface tension barrier is utilized in the instant invention, a brief discussion of the nature of surface tension will prove beneficial.

Whenever a mesh screen is partially immersed in a body of liquid and the adhesive forces between the material from which the screen is constructed and the liquid are greater than the cohesive forces inherent in the liquid, capillary action will be experienced. A portion of the liquid in the form of a thin film will migrate or spread upwardly across the screen covering individual pores of the screen. At a certain point above the liquid surface the migration will be terminated. The height or head of the liquid film will terminate when the adhesive forces promoting capillary action are counterbalanced by the combined forces of gravity and potential energy of the mass of liquid constituting the film. The height of film for the particular environment defines the head holding ca pacity of the screen. This is primarily a function of the (1) inherent adhesive forces of the materials, (2) the temperature, and (3) most important, for the purposes of this invention, the applied G force. An 8 micron mesh screen at +200 F. is capable of supporting a ten-inch head of C-lF in a 1G field. When the G force is increased, then the maximum supportable liquid head is correspondingly decreased. Thus, the capacity to maintain a liquid head is inversely proportional to the G force being exerted on the screen.

Referring again to FIG. 2 the surface tension barrier is represented by zone 62 which overlays that portion of the surface area of screen 40 between liquid surface and inlet 35. Zone 69 indicates a liquid permeable portion of screen 4%) lying between liquid surface 55 and rear wall 27. Bubbles from the pocket of gas 5'3 are at all times attempting to break through and rupture the surface tension barrier of zone 62. The head of liquid which must be supported on screen 40 in order to prevent rupturing of the surface tension barrier is indicated by letter l-l. Head l-l represents the greatest distance between liquid surface 55 and that portion of screen 40 adjacent forward wall 26 multiplied by the G force G The pore size of screen 4% and the dimensions and configuration of small tank 22 are especially designed to assure that the surface tension barrier will be capable of withstanding the most adverse cumulative forces resulting from gravity force G and the forces exerted by pressurant gas 53. As indicated by flow arrows 65, liquid 50 collected in reservoir 42 is forced by pressurant gas 53 to flow in a continuous uninterrupted stream through the pores in zone 60, shallow chamber 46, outlet line 34 and eventually to a remote location (not shown).

In FIG. 1, no surface tension barrier is needed in screen trap 2t) to achieve a smooth, uninterrupted discharge of bubble free and otherwise uncontaminated liquid 50. The entire screen 4% is liquid penmeable as in the case of zone 60, as shown in FIG. 2. Thus under the conditions depicted in FIG. 1, pressurant gas 52 forces liquid 50 through inlet line 30, screen 40 and finally through outlet line 34.

As previously mentioned, the maximum volume of liquid 50 to be expelled is controlled by the dimensions and configuration of main tank 12 and is in no way influenced by the dimensions and configuration of screen trap 29. If there were no screen trap 20, as is the case with conventional expulsion devices, and a screen capable of developing a surface tension barrier lined the interior of main tank 12, then the maximum volume of fluid to be ex elled would be a function of and directly controlled by the head holding capacity of the screen. In the instant invention these two features are independent of one another.

Another feature of the instant invention is illustrated in FIG. 3 wherein the expulsion device is shown being subjected to a gravity force G acting in a direction as indicated by the arrow. Under the influence of gravitational force G liquid 50 has been shifted to the forward end 16 of main tank It and in a similar manner the liquid 50 in screen trap 20 has been forced toward forward wall 26. This condition could occur, for example, when the expulsion device 10 is incorporated in a tactical missile or the like of the air-to-ground or air-to-air type and the missile at a point in time along its trajectory on route to a target is caused to pitch-over. Thus, at some point in time during an abrupt pitch-over of expulsion device 10, fluid 50 is, at least for a brief time, driven forwardly. In conventional expulsion tanks, the desired continuous outward flow of fluid 50 would be interrupted because the outlet opening would be exposed to the pressurant gas rather than it being in direct communication with the liquid. However, such flow interruptions are avoided by the instant invention due to the fact that a charge of fluid 50 is collected in reservoir 42. During pitch-over the pressurant gas is constantly forcing liquid 50 through the pores of screen 40 and outwardly through outlet line 34. As the supply of liquid 50 in reservoir 42 gradually becomes depleted, the expulsion device It) is recovering from the pitch-over motion and liquid St], under a programmed type trajectory, will be shifted toward the rearward end 17 of main tank 12. Then with the remaining supply of liquid 50, once again in direct communication with inlet opening 31, such liquid will be continuously discharged through screen trap 20 in a manner as described with regard to either FIG. 1 or FIG. 2.

Due to the fact that the path of motion for expulsion device 10 will be programmed, virtually all of the liquid 50 will be admitted into reservoir 42 by way of inlet line 30. Under these ideal circumstances, the only amount of liquid that will not be discharged from screen trap 29 is the fluid occupying the volume in shallow chamber 46. The pressurant gas 52, as previously indicated, is unable to rupture the surface tension barrier existing on screen 49 and therefore this minimal quantity of fluid cannot be expelled.

The resultant G forces G G and G shown in FIGS. 1, 2, and 3, respectively, illustrate how smooth, continuous flow of liquid 50 is achieved as the expulsion device 10 experiences broadly varying gravitational effects. It should be noted that expulsion tank 10 is designed in a manner such that while it is at any stage in its predetermined flight trajectory, flow through screen trap 20 cannot be interrupted. Expulsion device 10 possesses the advantages arising from utilizing a surface tension barrier in screen trap 20 and utilizing a large volume in main tank 12 whose configuration and volume is wholly independent from the volume and configuration of screen trap 20. The components of expulsion device 10 are held in fixed relationship relative to one another and therefore the usual disadvantages associated with moving parts are avoided. Expulsion tank 10 can be reused numerous times. Thus, tests can be conducted on a particular ex- 'pulsion device 10 before it is used in an actual mission.

Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is by Way of illustration and example only, and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claims.

I claim:

1. A fluid expulsion device comprising:

a first tank for containing gas-pressurized liquid to be expelled,

a second tank disposed inside the first tank,

a screen disposed within said second tank adjacent an interior wall thereof, the screen having a mesh suflicient to produce a surface tension barrier for blocking penetration of bubbles from a pressurant gas contained in said first tank through the barrier, the head holding capacity of the barrier being independent of the volume of said first tank, and,

means for conducting the fluid from the first tank, through the second tank including said screen and outwardly of both tanks.

2. The structure according to claim 1 wherein the means for conducting the fluid includes a fluid line extending between the first and second tanks, and a second fluid line extending between the second tank and a point outside both tanks.

3. The structure according to claim 2 wherein the end of the second fluid line inside the second tank is connected in fluid-tight relationship to the screen.

4. The structure according to claim 3 wherein a space is defined by the screen and adjacent Wall of the second tank to provide a shallow chamber through Which fluid being expelled is conducted to the second fluid line.

5. The structure according to claim 3 wherein an edge of the screen is attached in fluid-tight relationship to a wall section of the second tank.

6. A fluid expulsion device comprising:

a first tank for containing gas-pressurized fluid to be expelled,

a second tank disposed inside the first tank, the respective volumes of the tanks being independent of one another,

a screen disposed adjacent the interior Wall of the second tank,

the screen having a mesh suflicient to produce a surface tension barrier for blocking penetration of bubbles from a pressurant gas through the screen,

a reservoir for collecting fluid defined by an interior surface of the screen and the wall of the second tank,

a shallow chamber defined by an exterior surface of the screen and an adjacent Wall portion of this second tank, and,

means for conducting the fluid successively from said first tank, through said reservoir and shallow chamber, and then outwardly of both tanks.

7. The method of expelling fluid from an expulsion device comprising:

providing a first volume of liquid to be expelled,

maintaining gas pressure on said liquid,

providing a second volume inside of said first volume, the gas pressure forcing said liquid from said first to said second volume,

providing a third volume adjacent said second volume,

forcing said liquid from said second volume to said third voiume,

maintaining a surface tension barrier on a screen disposed between said second and third volumes to block passage of gas between said volumes, the head holding capacity of the barrier being independent of said first volume, and,

forcing said liquid from said third volume out of the device.

References Cited UNITED STATES PATENTS 2,645,381 7/1953 Lattman 222-189 2,774,628 12/1956 Engstrum 222-189 2,961,064 11/1960 Fisher 466 X 3,273,313 9/1966 Livesey et al. 5546 STANLEY H. TOLLBERG, Primary Examiner. 

